Tag: sperm

One night of passion and you’re filled with a lifetime full of sperm with no need to ever mate again. As sex lives go, it doesn’t sound very appealing, but it’s what many ants, bees, wasps and termites experience. The queens of these social insects mate in a single “nuptial flight” that lasts for a few hours or days. They store the sperm from their suitors and use it to slowly fertilise their eggs over the rest of their lives. Males have this one and only shot at joining the Mile High Club and they compete fiercely for their chance to inseminate the queen. But even for the victors, the war isn’t over. Inside the queen’s body, their sperm continue the battle.

If the queen mates with several males during her maiden flight, the sperm of each individual find themselves swimming among competitors, and that can’t be tolerated. Susanne den Boer from the University of Copenhagen has found that these insects have evolved seminal fluids that can incapacitate the sperm of rivals while leaving their own guys unharmed. And in some species, like leafcutter ants, the queen steps into the fray herself, secreting chemicals that pacify the warring sperm and ease their competition.

The amazing thing about this chemical warfare is that it has evolved independently several times. Social insects evolved from ancestors that observed strictly monogamous relationships. Even now, the queens from many species mate with just one male during their entire lives. With just one set of sperm in their bodies, they have no problem with sperm conflict. The trouble starts when species start mating with several males during their nuptial flights, as honeybees, social wasps, leafcutter ants, army ants, and others do today.

Okutsu works on salmonids, a group of fish that includes salmon and trout. Many members of this tasty clan have suffered greatly from over-fishing in the last few decades, and their populations are dwindling their way to extinction.

If stocks fall below a critical level, they may need a jump-start. One strategy is to freeze some eggs to be fertilised artificially, in the way that many human eggs are in fertility clinics. But it’s much harder for fish eggs – they are large and have lots of fat, which makes them difficult to freeze effectively.

Okutsu’s group have hit on a more effective solution. They use transplanted sexual stem cells to turn another species of fish into surrogate parents for the endangered ones.